Improvement in mariners  compasses



' J. A. MARDEN. Mariners-Oompass.

No. 198,132. Patented Dec. 1 1,l877

1 which is composed of a short rod of steel north poles at their upperends, while those of the opposite quadrants, or those flanking the northpole of the needle, shall have their pass-card, and B its magneticneedle, the lat- UNITED STATES PATENT OFFI E;

. JEREMIAH A; MARDEN, OF

BOSTON, MASSACHUSETTS.

IMPROVEMENT IN MARINERVS COMPASSES.

Specification forming part of Letters Patent No. 198,132, dated December11, 1877 application filed November 20,1877.

To all whom it may concern:

Be it known that I, JEREMIAH A. MARDEN, of Boston, of the county ofSuffolk and State of Massachusetts, have invented a new and usefulImprovement in the Mariners Oompass and do hereby declare the same to befully described in the following specification and represented in theaccompanying drawings, of whichj Figure l is a top view, and Fig. 2 atransverse section, of a compass provided with my invention. Fig. 3 is aside view, and Fig. 4 a bottom view, of the compass-card, magneticneedle, and their additions, as hereinafter explained.

The main purpose of my invention is to prevent the needle from beingdeflected from its true course by any iron or metal in its vicinity,especially when the compass is in use on shipboard.

To this end I combine with the magnetic needle, or with such and itscard, a circular range or series of vertical magnets, each of hardenedat and near its upper end only, such magnets being so arranged thatthose which may be in the quadrants flanking the south pole of theneedle shall have their south poles at their upperends.

With such a needle and series of surrounding magnets, or with them andthe card, I combine a suitable float, which, as shown in the drawings,is an annulus of cork, its buoyant power being sufficient tocounterbalance, or nearly counterbalance, the weight of the needle andthe series of magnets, or such and the card. I

In the drawings, A denotes a common comter being extended diametricallyacross a float, G, upon which the card is fixed concentrically. There isinserted vertically in such float a circular range or series of shortrods or bar-magnets, D D D, &c., they being disposed at or about equaldistances apart. Each of these magnets is to be a steel bar hardened atand near its upper end only, the rest of the bar being left in its softor normal condition, or not hardened, in order that going at rightangles to the needle throughits center, or which are beneath the northsemicircl'e'of the card, should have their south poles uppermost, therest of the magnets havin g their north poles uppermost. I

In consequence of this construction of magnets and arrangement of themwith the magnetized needle, or such and its card, such needle will haveits south pole flanked or guarded on both sides by the north poles ofthe semicircular range of magnets, the other pole of the magnetic needlebeing similarly flanked or guarded by the south poles of the remainingmagnets. Therefore, should there be in the vicinity of the needle a massor object of iron tending to attract the needle at its south pole, so asto draw it out of the magnetic meridian, the force of attraction will becounteracted by the repellent powers of thenorth poles of the adjacentflanking magnets 5 so, should the needle at its north pole be subjectedto an attraction tending to deflect it from the meridian, the adjacentflanking magnets will counteract such attraction, all of which I havedemonstrated in practice.

The needle, its float, and repellent magnets are'to be arranged withinwater, or a suitable liquid, in a bowl, E, having projecting up from itsbottom a post, F, carrying the pivot a of the needle.

The additional or repellent magnets, the needle, and the float, or suchand the card, I usually coverwith a varnish or substance resistive ofthe oxidizing powers .of the said liquid.

I claim- 1. The combination of the magnetic needle and a circular rangeor series of magnets, constructed and having their poles arranged withthose of such needle, substantially as set forth.

2. The combination of the float, the magnetic needle, and. theeireularrange :01 series arranged with those of such needle, substanof magnets,constructed and having their poles tial ly :as set forth.

arranged with those of such needle substantially as set forth. 7JEREMIAH MARDEN' 3. The combination of the compass-card,

the magnetic needle, the float, and. the series;

of magnets, constructed. and having their poles Witnesses R. ,H. EDDY,JOHN Snow.

